Assassin's Reward - worth it?

My thief is level 50 so I've been experimenting with traits a bit. So far I'm digging D/D + P/P for open world PvE with a focus on stealth and mobility, so most of my points are in Shadow Arts and Acrobatics. Assassin's Reward looked like a fun trait that does exactly what I was looking for (staying power over the course of a fight) but I gotta say, it feels like it does nothing. I've tried switching it off and on and it's really hard to notice a difference (I see my health bar going up, but not as much as I'd like).

Does the trait become better at higher levels? Do I need to build differently to take advantage of it better? Or am I just not noticing it?